The overall objectives of this project were to determine the importance of DNA repair to both the development of cancer and cancer therapy. Specifically, we are studying a variety of DNA repair inhibitors to localize their effects with respect to repair pathway inhibited and the specific steps inhibited so that these agents may be used as tools to study the biological significance of DNA repair. Goals for the current year include: the use of photoaffinity labeling as a new technique for studying DNA repair; localization of the specific repair steps with respect to pathway and enzyme involved; and the clear identification of the loci of inhibitor effects. BIBLIOGRAPHIC REFERENCES: Yielding, L.W., White, W.E., Jr., and Yielding, K.L. "Production of Frameshift Mutations in Salmonella by a Light Sensitive Azide Analog of Ethidium" Mut. Res. 34: 351-358 (1976). Nishida, M., Nakamura, N., and Yielding, K.L. "Inhibition by Nalidixic Acid of Post UV survival of E. coli" Proc. Exp. Biol. Med. 151: 271-274 (1976).